The invention put forward here consists of an electro-stunning and/or electro-sacrifice procedure, mainly for industrial application to ichthyiological species in floating cages, from among those means of electro-stunning and/or electro-sacrifice of animal species.
This does not mean that it cannot be applied to any confinement structure, raising and fattening of fish, such as rigid cages, fixed bottom cages, cages formed by closing off bays, between islands, between island and coast, etc. as well as in fish nurseries on land, swimming pools, large aquariums, brooks and artificial lakes.
Independently of the possibility of extension of this technique to other ichthyiological species, preferably marine species, this process is basically designed for preferred application to fishes of the broad family of mackerel, such as all types of tuna fish, bonito, the sword fish, etc.
This does not mean that it cannot be used with other species of fish.
In order to optimise the productivity during the sacrifice of the fish, to maintain the quality of the fish meat after this sacrifice and, finally, to maintain this quality in a controlled fashion a posteriori, this invention takes special advantage of floating cages for holding and fattening fish and, in general, it takes special advantage of any confinement system in which two divers, one a hunter and the other a controller can enter, who use a modified harpoon along with equipment for conversion of electrical potential, connected to a submerged plate to introduce an electrical signal into the fish that stuns or kills it.
Afterwards, the fish is equipped with an identification label recording all the incidences in the manipulation of the animal, recovering the harpoon with its corresponding rifle towards the boat.
Currently the tuna fish are sacrificed from the boats by lifting the bottom of the floating cage and firing a shotgun or hitting them over the head with a club. This grouping of fish in a minimal vital space and the killing itself produce a high degree of stress and cause metabolic processes that alter the quality of the fish meat.
With regards to the alteration of the quality of the fish meat produced by stress before death, biochemical and physiological aspects should be considered.
Thus, most fish, as is the case for many animal species, show a reaction of maximum energy in the face of any stress, fright or danger, such as when they are withdrawn alive from the water. Normally, the reaction consists of changes in the heart rhythm; an increase in cortisol, adrenaline and noradrenaline production, as well as vigorous muscle contractions. These processes are stronger still when the fish fight for a long time against a slow death.
This effort depletes the oxygen reserves in the muscles, and so the normal aerobic glycolysis of glycogen sugar cannot take place to release energy resources in the form of ATP molecules. Therefore the muscles have to resort anaerobic glycolysis for the production of ATP. This process leads to an accumulation of lactic acid with a reduction in the pH of the muscles, and a drop in the energy resources thereof (glycogen and ATP).
The overall result of these effects is an acceleration in the autolytical spoliation in the cellular environment after death, which increases bacterial degradation.
Almost all the methods existing for capturing and sacrificing fish lead to greater or lesser stress levels and so different levels of reduction in the quality and consistency of the product are observed. When, after death, the fish is not cooled rapidly, the meat begins to soften and spoil with denaturing of the proteins, liquid loss, loss of the integrity of the muscular tissue, change of colour through diffusion of haemoproteins. On the other hand, the lipids are hydrolysed and oxidised.
Measurement of the pH in recently cut muscles provide reliable indications of the levels of lactic acid and stress suffered during the capture and sacrifice. If the pH is 7 or less this indicates that the fish has suffered from a lot of stress, which has led to the high levels of lactic acid.
The applicant is unaware of the existence of electro-stunning and/or electro-sacrifice in floating cages and confinement structures in general with the characteristics that will now be described.
When tackling the problem of exploitation of marine ichthyological species, such as the red tuns, Thunnus Thynnus (and also other ichthyoloigcal varieties and species), kept and fed in floating cages, in order to guarantee that good results are obtained for this activity, three indispensable aspects should be considered.
1) The need to guarantee the realisation of the sacrifice of the ichthyiological species, object of this exploitation, in conditions that guarantee that no biochemical, hormonal or mechanical or any other type of alteration that might lead to a reduction in the quality of the fish meat, reducing its economical value in the market, is produced in fish meat of said species.
2) The need that the chosen sacrifice system, with respect to the number of fish sacrificed per hour, guarantees a high productivity and, all this with the aim of reducing the processing time of the batch of tuna fish and, also, preventing the production costs from rising, keeping them within a level that competes with the market prices.
3) The need to ensure that, in order to control and guarantee the quality of the meat product obtained, each fish should be identified with a code that allows it to be monitored for quality throughout the productive process.
These three requirements are broadly met with the proposed system.
The invention object of the present specification relates to the fact that, in a cage or confinement structure with fish, two divers are introduced, the hunter armed with a rifle with modified harpoon, with one or two electrodes, equipped or not equipped with sensors and connected to equipment for transforming electrical potential, connected to a submerged plate.
The other diver, the controller, is the one who activates the switch of the equipment that sends an electrical signal that stuns or kills the fish to the plate and the tip of the harpoon. The fish is caught with a rope and pulled from the water by a crane and given a plastic identifying label. The rifle and harpoon are recovered and taken to the boat.